DNA amplification techniques are widely utilized in the fields of bioscience, genetic engineering and medicine for the purposes of research, development and diagnosis. Especially, the DNA amplification technique based on polymerase chain reaction (PCR) is widely employed. PCR is used to amplify a particular DNA sequence as desired. The first step of PCR is to denature DNA. A double-stranded DNA is split by heating. Each separated DNA strand serves as a template. The second step of PCR is annealing. In this step, primers are annealed to the template DNA. The annealing temperature is an important factor determining the accuracy of the reaction. If the temperature is too high, the quantity of amplified DNA products decreases drastically because the primers are too weakly bound to the template DNA. And, if the temperature is too low, unwanted DNA may be amplified due to nonspecific binding of the primers. The third PCR step of PCR is elongation. At this step, a thermostable DNA polymerase synthesizes new DNA from the template DNA. The PCR may be classified into DNA PCR and RNA PCR. Usually, the purpose of amplifying genes by PCR is to observe particular sequences in the genes, not the entire genes. In such PCR techniques, it is very important to form accurate temperature gradients for the respective PCR steps and to maintain them.